1.Field of the Invention
The present invention relates to a method and apparatus for handling tools of substantial longitudinal length to insert the tools into and withdraw them from a pressurized container, such as a well bore.
2.Description of the Prior Art
It is necessary to periodically monitor the conditions within a producing well and, for this reason, logging tools are sent downhole on a wireline to gather the necessary data. There are two problems that are involved in accomplishing this data collection, namely, the tools are elongated tubular assemblies of relatively small diameter, in comparison their length, fashioned from short lengths of tubular members to form a single tool of perhaps 20 to 60 feet in length. At this point, it becomes quie evident that the tool will be quite difficult to handle because of its length. The tool is introduced to the well by attaching a lubricator to a blowout preventer at the top of the well casing. The lubricator is a series of large diameter tubular members assembled around the logging tool and contains, at its upper end, a grease injection tube or stuffing box through which the wireline for suspending the tool is passed. The lubricator itself is a major handling problem since it is long, heavy, difficult to manipulate in the rig and make connections, and it also is expensive. After the lubricator and stuffing box have been assembled about the tool, and the tool attached to the wireline, the assembly of the tool and lubricator is hoisted into position on the blowout preventer and secured thereto. Pressure between the borehole and lubricator is equalized by opening a bypass valve around the blowout preventer. The blowout preventer is then opened allowing access to the borehole. After the blowout preventer has been opened, the tool can be lowered into the borehole by the wireline with the grease injection tube or stuffing box providing a seal around the wireline as the tool is lowered.
The tool is extracted from the borehole by drawing it up to a position within the lubricator, closing the blowout preventer, venting the lubricator, and removing the assembly of the tool and lubricator from the blowout preventer and lowering them to a position where they can be subsequently disassembled into the individual components. It will be appreciated from the foregoing description that there are a number of difficulties in such an opertion, including knowing when the tool has been fully withdrawn into the lubricator, not drawing the wireline so taut against the stuffing box that there is a possibility of the wireline being broken with the result being the tool falling downhole before the blowout preventer can be closed and closing the blowout preventer on the tool before it is fully withdrawn into the lubricator. Of course handling the lubricator and tool during the extraction process is equally as difficult as handling them during the insertion process.